1. Field of the Invention
The present invention relates to an improved coal liquefaction process. More particularly, the invention relates to a process comprising pretreatment of a coal liquefaction chargestock followed by coal liquefaction.
2. Description of the Prior Art
Coal liquefaction processes in which coal with or without a diluent is subjected to elevated temperatures and pressures to convert the coal to normally liquid hydrocarbonaceous products are well known. Coal liquefaction processes in which coal is converted in the presence of a hydrogen donor diluent with or without added hydrogen are also known. See for example U.S. Pat. No. 3,645,885 and U.S. Pat. No. 3,617,513, the teachings of which are hereby incorporated by reference.
U.S. Pat. No. 3,303,126 discloses a non-catalytic hydrorefining process for hydrocarbonaceous oils in which a mixture of hydrogen and hydrogen sulfide is utilized.
U.S. Pat. No. 3,271,302 discloses pretreatment of a hydrocarbon oil feed with hydrogen and hydrogen sulfide followed by catalytic hydrorefining.
U.S. Pat. No. 3,503,863 discloses the addition of hydrogen sulfide to a hydrogen donor solvent coal liquefaction process.
It has now been found that pretreatment of the coal liquefaction feed with a hydrogen sulfide-containing gas for a specific residence time at a given temperature gives improved coal liquefaction results such as coke suppression and an increase of liquid yield.